Protein kinases constitute a large family of structurally related enzymes that are responsible for the control of a variety of signal transduction processes within the cell. Protein kinases, containing a similar 250-300 amino acid catalytic domain, catalyze the phosphorylation of target protein substrates.
The kinases may be categorized into families by the substrates in the phosphorylate (e.g., protein-tyrosine, protein-serine/threonine, lipids, etc.). Tyrosine phosphorylation is a central event in the regulation of a variety of biological processes such as cell proliferation, migration, differentiation and survival. Several families of receptor and non-receptor tyrosine kinases control these events by catalyzing the transfer of phosphate from ATP to a tyrosine residue of specific cell protein targets. Sequence motifs have been identified that generally correspond to each of these kinase families [Hanks et al., FASEB J., (1995), 9, 576-596; Knighton et al., Science, (1991), 253, 407-414; Garcia-Bustos et al., EMBO J., (1994), 13:2352-2361). Examples of kinases in the protein kinase family include, without limitation, ab1, Akt, bcr-ab1, Blk, Brk, Btk, c-kit, c-Met, c-src, c-fns, CDK1, CDK2, CDK3, CDK4, CDK5, CDK6, CDK7, CDK8, CDK9, CDK10, cRaf1, CSF1R, CSK, EGFR, ErbB2, ErbB3, ErbB4, Erk, Fak, fes, FGFR1, FGFR2, FGFR3, FGFR4, FGFR5, Fgr, fit-1, Fps, Frk, Fyn, Hck, IGF-1R, INS-R, Jak, KDR, Lck, Lyn, MEK, p38, PDGFR, PIK, PKC, PYK2, ros, Tie, Tie-2, TRK, Yes, and Zap70.
Studies indicated that protein kinases play a central role in the regulation and maintenance of a wide variety of cellular processes and cellular function. For example, kinase activity acts as molecular switches regulating cell proliferation, activation, and/or differentiation. Uncontrolled or excessive kinase activity has been observed in many disease states including benign and malignant proliferation disorders as well as diseases resulting from inappropriate activation of the immune system (autoimmune disorders), allograft rejection, and graft vs host disease.
It is reported that many diseases are associated with abnormal cellular responses triggered by protein kinase-mediated events. These diseases include autoimmune diseases, inflammatory diseases, bone diseases, metabolic diseases, neurological and neurodegenerative diseases, cancer, cardiovascular diseases, allergies and asthma, Alzheimer's disease and hormone-related diseases. In addition, endothelial cell specific receptor PTKs, such as VEGF-2 and Tie-2, mediate the angiogenic process and are involved in supporting the progression of cancers and other diseases involving uncontrolled vascularization. Accordingly, there has been a substantial effort in medicinal chemistry to find protein kinase inhibitors that are effective as therapeutic agents.
One kinase family of particular interest is the Src family of kinases, Src kinase is involved in proliferation and migration responses in many cell types, cell activation, adhesion, motility, and survival, growth factor receptor signaling, and osteoclast activation (Biscardi et al., Adv. Cancer Res. (1999), 76, 61-119; Yeatman et al., Nat. Rev. Cancer (2004), 4, 470-480; Owens, D. W.; McLean et al., Mol. Biol. Cell (2000), 11, 51-64). Members of the Src family include the following eight kinases in mammals: Src, Fyn, Yes, Fgr, Lyn, Hck, Lck, and Blk (Bolen et al., Annu. Rev. Immunol, (1997), 15, 371). These are nonreceptor protein kinases that range in molecular mass from 52 to 62 kD. All are characterized by a common structural organization that is comprised of six distinct functional domains: Src homology domain 4 (SH4), a unique domain, SH3 domain, SH2 domain, a catalytic domain (SH1), and a C-terminal regulatory region (Brown et al., Biochim Biophys Acta (1996), 1287, 121-149; Tatosyan et al. Biochemisty (Moscow) 2000, 65, 49-58). SH4 domain contains the myristylation signals that guide the Src molecule to the cell membrane. This unique domain of Src proteins is responsible for their specific interaction with particular receptors and protein targets (Thomas et al., Annu Rev Cell Dev Biol (1997), 13, 513-609). The modulating regions, SH3 and SH2, control intra- as well as intermolecular interactions with protein substrates which affect Src catalytic activity, localisation and association with protein targets (Pawson T., Nature (1995), 373, 573-580). The kinase domain, SH1, found in all proteins of the Src family, is responsible for the tyrosine kinase activity and has a central role in binding of substrates. The N-terminal half of Src kinase contains the site(s) for its tyrosine phosphorylation and regulates the catalytic activity of Src (Thomas et al., Annu Rev Cell Dev Biol (1997), 13: 513-609). v-Src differs from cellular Src (c-Src) on the basis of the structural differences in C-terminal region responsible for regulation of kinase activity.
The prototype member of the Src family protein tyrosine kinases was originally identified as the transforming protein (v-Src) of the oncogenic retrovirus, Rous sarcoma virus, RSV (Brugge et al., Nature (1977), 269, 346-348); Hamaguchi et al. (1995), Oncogene 10: 1637-1043). Viral v-Src is a mutated and activated version of a normal cellular protein (c-Src) with intrinsic tyrosine kinase activity (Collett et al., Proc Natl Acad Sci USA (1978), 75, 2021-2024). This kinase phosphorylates its protein substrates exclusively on tyrosyl residues (Hunter et al., Proc Natl Acad Sci USA (1980), 77, 1311-1315).
Investigations indicated that Src is a cytoplasmic protein tyrosine kinase, whose activation and recruitment to perimembranal signaling complexes has important implications for cellular fate. It has well-documented that Src protein levels and Src kinase activity are significantly elevated in human breast cancers (Muthuswamy et al., Oncogene, (1995), 11, 1801-1810); Wang et al., Oncogene (1999), 18, 1227-1237; Warmuth et al., Curr. Pharm. Des. (2003), 9, 2043-2059], colon cancers (Irby et al., Nat Genet (1999), 21, 187-190), pancreatic cancers (Lutz et al., Biochem Biophys Res Commun (1998), 243, 503-508], certain B-cell leukemias and lymphomas (Talamonti et al., J. Clin. Invest. (1993), 91, 53; Lutz et al., Biochem. Biophys. Res. (1998), 243, 503; Biscardi et al., Adv. Cancer Res. (1999), 76, 61; Lynch et al., Leukemia (1993), 7, 1416; Boschelli et al., Drugs of the Future (2000), 25(7), 717), gastrointestinal cancer (Cartwright et al., Proc. Natl. Acad. Sci. USA, (1990), 87, 558-562 and Mao et al., Oncogene, (1997), 15, 3083-3090), non-small cell lung cancers (NSCLCs) (Mazurenko et al., European Journal of Cancer, (1992), 28, 372-7), bladder cancer (Fanning et al., Cancer Research, (1992), 52, 1457-62), oesophageal cancer (Jankowski et al., Gut, (1992), 33, 1033-8), prostate and ovarian cancer (Wiener et al., Clin. Cancer Research, (1999), 5, 2164-70), melanoma and sarcoma (Bohlen et al., Oncogene, (1993), 8, 2025-2031; Tatosyan et al., Biochemistry (Moscow) (2000), 65, 49-58). Furthermore, Src kinase modulates signal transduction through multiple oncogenic pathways, including EGFR, Her2/neu, PDGFR, FGFR, and VEGFR (Frame et al., Biochim. Biophys. Acta (2002), 1602, 114-130; Sakamoto et al., Jpn J Cancer Res, (2001), 92: 941-946).
Thus, it is anticipated that blocking signaling through the inhibition of the kinase activity of Src will be an effective means of modulating aberrant pathways that drive oncologic transformation of cells. Src kinase inhibitors may be useful anti-cancer agents (Abram et al., Exp. Cell Res., (2000), 254, 1). It is reported that inhibitors of src kinase had significant antiproliferative activity against cancer cell lines (M. M. Moasser et al., Cancer Res., (1999), 59, 6145; Tatosyan et al., Biochemistry (Moscow) (2000), 65, 49-58).) and inhibited the transformation of cells to an oncogenic phenotype (R. Karni et al., Oncogene (1999), 18, 4654). Furthermore, antisense Src expressed in ovarian and colon tumor cells has been shown to inhibit tumor growth (Wiener et al., Clin. Cancer Res., (1999), 5, 2164; Staley et al., Cell Growth Diff. (1997), 8, 269). Src kinase inhibitors have also been reported to be effective in an animal model of cerebral ischemia (Paul et al. Nature Medicine, (2001), 7, 222), suggesting that Src kinase inhibitors may be effective at limiting brain damage following stroke. Suppression of arthritic bone destruction has been achieved by the overexpression of CSK in rheumatoid synoviocytes and osteoclasts (Takayanagi et al., J. Clin. Invest. (1999), 104, 137). CSK, or C-terminal Src kinase, phosphorylates and thereby inhibits Src catalytic activity. This implies that Src inhibition may prevent joint destruction that is characteristic in patients suffering from rheumatoid arthritis (Boschelli et al., Drugs of the Future (2000), 25(7), 717).
It is well documented that Src-family kinases are also important for signaling downstream of other immune cell receptors. Fyn, like Lck, is involved in TCR signaling in T cells (Appleby et al., Cell, (1992), 70, 751). Hck and Fgr are involved in Fcγ receptor signaling leading to neutrophil activation (Vicentini et al., J. Immunol. (2002), 168, 6446). Lyn and Src also participate in Fcγ receptor signaling leading to release of histamine and other allergic mediators (Turner, H. and Kinet, J-P Nature (1999), 402, B24). These findings suggest that Src family kinase inhibitors may be useful in treating allergic diseases and asthma.
Other Src family kinases are also potential therapeutic targets. Lck plays a role in T-cell signaling. Mice that lack the Lck gene have a poor ability to develop thymocytes. The function of Lck as a positive activator of T-cell signaling suggests that Lck inhibitors may be useful for treating autoimmune disease such as rheumatoid arthritis (Molina et al., Nature, (1992), 357, 161).
Hck is a member of the Src protein-tyrosine kinase family and is expressed strongly in macrophages, an important HIV target cell and its inhibition in HIV-infected macrophages might slow disease progression (Ye et al., Biochemistry, (2004), 43 (50), 15775-15784).
Hck, Fgr and Lyn have been identified as important mediators of integrin signaling in myeloid leukocytes (Lowell et al., J. Leukoc. Biol., (1999), 65, 313). Inhibition of these kinase mediators may therefore be useful for treating inflammation (Boschelli et al., Drugs of the Future (2000), 25(7), 717).
It is reported that Syk is a tyrosine kinase that plays a critical role in the cell degranulation and eosinophil activation and Syk kinase is implicated in various allergic disorders, in particular asthma (Taylor et al., Mol. Cell. Biol. (1995), 15, 4149).
BCR-ABL encodes the BCR-AEL protein, a constitutively active cytoplasmic tyrosine kinase present in 90% of all patients with chronic myelogenous leukemia (CML) and in 15-30% of adult patients with acute lymphoblastic leukemia (ALL). Numerous studies have demonstrated that the activity of BCR-ABL is required for the cancer causing ability of this chimeric protein.
Src kinases play a role in the replication of hepatitis B virus. The virally encoded transcription factor HBx activates Src in a step required for propagation of the virus (Klein et al., EMBO J. (1999), 18, 5019; Klein et al., Mol. Cell. Biol. (1997), 17, 6427). Some genetic and biochemical data clearly demonstrate that Src-family tyrosine kinases serve as a critical signal relay, via phosphorylation of c-Cbl, for fat accumulation, and provide potential new strategies for treating obesity (Sun et al., Biochemistry, (2005), 44 (44), 14455-14462). Since Src plays a role in additional signaling pathways, Src inhibitors are also being pursued for the treatment of other diseases including osteoporosis and stroke (Susva et al., Trends Pharmacol. Sci. (2000), 21, 489-495; Paul et al., Nat. Med. (2001), 7, 222-227).
It is also possible that inhibitors of the Src kinase activity are useful in the treatment of osteoporosis (Soriano et al., Cell (1991), 64, 693; Boyce et al. J. Clin. Invest (1992), 90, 1622; Owens et al., Mol. Biol. Cell (2000), 11, 51-64), T cell mediated inflammation (Anderson et al., Adv. Immunol. (1994), 56, 151; Goldman, F D et al. J. Clin. Invest. (1998), 102, 421), and cerebral ischemia (Paul et al. Nature Medicine (2001), 7, 222).
In addition, src family kinases participate in signal transduction in several cell types. For example, fyn, like Ick, is involved in T-cell activation. Hck and fgr are involved in Fe gamma receptor mediated oxidative burst of neutrophils. Src and lyn are believed to be important in Fc epsilon induced degranulation of mast cells, and so may play a role in asthma and other allergic diseases. The kinase lyn is known to be involved in the cellular response to DNA damage induced by UV light (Hiwasa et al., FEBS Lett. (1999), 444, 173) or ionizing radiation (Kumar et al., J Biol Chein, (1998), 273, 25654). Inhibitors of lyn kinase may thus be useful as potentiators in radiation therapy.
T cells play a pivotal role in the regulation of immune responses and are important for establishing immunity to pathogens. In addition, T cells are often activated during inflammatory autoimmune diseases, such as rheumatoid arthritis, inflammatory bowel disease, type I diabetes, multiple sclerosis, Sjogren's disease, myasthenia gravis, psoriasis, and lupus. T cell activation is also an important component of transplant rejection, allergic reactions, and asthma.
T cells are activated by specific antigens through the T cell receptor, which is expressed on the cell surface. This activation triggers a series of intracellular signaling cascades mediated by enzymes expressed within the cell (Kane et al. Current. Opinion in Immunol. (2000), 12, 242), These cascades lead to gene regulation events that result in the production of cytokines, like interleukin-2 (IL-2). IL-2 is a necessary cytokine in T cell activation, leading to proliferation and amplification of specific immune responses.
Therefore, Src kinase other kinase have become an intriguing target for drug discovery (Parang et al., Expert Opin. Ther. Pat. (2005), 15, 1183-1207; Parang et al., Curr. Opin. Drug Discovery Dev. (2004), 7, 630-638). Many classes of compounds have been disclosed to modulate or, more specifically, inhibit kinase activity for use to treat kinase-related conditions or other disorders. For example, U.S. Pat. No. 6,596,746 and the PCT WO 05/096784A2 disclosed benzotrianes as inhibitors of kinases; the PCT WO 01/81311 disclosed substituted benzoic acid amides for the inhibition of angiogenisis; U.S. Pat. No. 6,440,965, disclosed substituted pyrimidine derivatives in the treatment of neurodegenerative or neurological disorders; PCT WO 02/08205 reported the pyrimidine derivatives having neurotrophic activity; PCT WO 03/014111 disclosed arylpiperazines and arylpiperidines and their use as metalloproteinase inhibiting agents; PCT WO 03/024448 described compounds as inhibitors of histone deacetylase enzymatic activity; PCT WO 04/058776 disclosed compounds which possess anti-angiogenic activity. PCT WO 01/94341 and WO 02/16352 disclosed Src kinase inhibitors of quinazoline derivatives. PCT WO03/026666A1 and WO03/018021A1 disclosed pyrimidinyl derivatives as kinase inhibitors. U.S. Pat. No. 6,498,165 reported Src kinase inhibitor compounds of pyrimidine compounds. Peptides as Src Tyrosine Kinase Inhibitors is reported recently (Kumar et al., J. Med. Chem., (2006), 49 (11), 3395-3401). The quinolinecarbonitriles derivatives was reported to be potent dual Inhibitors of Src and Abl Kinases (Diane et al., J. Med. Chem., (2004), 47 (7), 1599-1601).
Although a lot of inhibitors of kinases are reported, considering the lack of currently available treatment options for the majority of the conditions associated with protein kinases, there is still a great need for new therapeutic agents that inhibit these protein targets.